Molecules intercalating two-dimensional (2D) materials form complex structures that have been mostly characterized by spatially averaged techniques. Here we use aberration-corrected scanning transmission electron microscopy and density-functional-theory (DFT) calculations to study the atomic structure of bilayer graphene (BLG) and few-layer graphene (FLG) intercalated with FeCl3. In BLG we discover two distinct intercalated structures that we identify as monolayer-FeCl3 and monolayer-FeCl2. The two structures are separated by atomically sharp boundaries and induce large but different free-carrier densities in the graphene layers, 7.1×1013 cm−2 and 7.1×1013 cm−2 respectively. In FLG, we observe multiple FeCl3 layers stacked in a variety of possible configurations with respect to one another. Finally, we find that the microscope's electron beam can convert the FeCl3 monolayer into FeOCl monolayers in a rectangular lattice. These results reveal the need for a combination of atomically-resolved microscopy, spectroscopy, and DFT calculations to identify intercalated structures and study their properties.
@article{arxiv.1903.00753,
title = {Atomic-Resolution Visualization and Doping Effects of Complex Structures in Intercalated Bilayer Graphene},
author = {Jason P. Bonacum and Andrew O'Hara and De-Liang Bao and Oleg S. Ovchinnikov and Yan-Fang Zhang and Georgy Gordeev and Sonakshi Arora and Stephanie Reich and Juan-Carlos Idrobo and Richard F. Haglund and Sokrates T. Pantelides and Kirill Bolotin},
journal= {arXiv preprint arXiv:1903.00753},
year = {2019}
}